For example, as shown in FIG. 24, a fuel battery has flat plates such as collector electrodes (separators) 2, an ion exchange membrane 3 held between them, membrane fixing reaction electrodes 4 fixed to the ion exchange membrane 3 and the like, and these constituting elements are combined, whereby a fuel battery cell 1 is constituted. As a material of the flat plates, a graphite or the like is employed in addition to a carbon, and further, a conductive resin such as a conductive phenol, an ion exchange resin, a metal such as a stainless steel, a magnesium alloy or the like, and the like may be employed.
With respect to a seal for the fuel battery cell 1 and a seal between the respective constituting elements, since a lot of seals are used for laminating a lot of cells 1, it is possible to make a product itself compact by using a seal material which is as thin or narrow as possible.
Further, there have been conventionally known a structure using a single gasket (refer to Japanese Unexamined Patent Publication No. 9-231987, 7-226220 or 7-153480), a structure in which a foamed sponge layer 6 is overlapped on a rubber plate 5 as illustrated so as to utilize as a gasket (refer to Japanese Unexamined Patent Publication No. 7-312223) and the like, however, these prior arts do not correspond to a structure intending to achieve objects of making the seal portion thin, improving an assembling property, preventing a position shift, making a surface pressure low, making the surface pressure uniform and the like, that is, these conventional separated type gasket has a disadvantage which can not sufficiently satisfy the points of making the seal portion thin, improving the assembling property, preventing the position shift, making the surface pressure low, making the surface pressure uniform and the like, and further, there is a risk that a problem in an assembling process, a malfunction due to a mis-assembling, a functional unstableness or the like is generated.
That is, in the case of a normal separated type gasket, although the low surface pressure, the uniform surface pressure and the like can be achieved, it has been impossible to simultaneously satisfy the thinness of seal, the position shift prevention at a time of assembling and the like.
Further, in the case of forming the gasket in accordance with the known forming method, a weld defect is easily generated in a terminal end portion of a material flow passage, so that it is hard to form a lip in the portion in correspondence to a shape of a metal mold, and this becomes the worst reason for obstructing a sealing performance.
Accordingly, in order to prevent the problems mentioned above, a vacuum forming is generally executed, and, in the conventional vacuum forming methods, there are a method of executing an evacuation by providing an evacuation passage in the middle of a material flow passage, and a method of executing an evacuation by surrounding a whole of a metal mold by a vacuum chamber.
However, in the former method, since there is a case that a low viscosity material corresponding to a forming material for a gasket flows in the evacuating passage, there is a problem that a stable formation of the gasket is obstructed. Further, in the latter method, there is a problem that a structure of the metal mold portion is necessarily complex and expensive, and further, there is a problem that an evacuating capacity becomes too much so as to give a bad influence to a cycle time.
The present invention is made by taking the points mentioned above into consideration, and an object of the present invention is to provide a gasket used for a fuel battery which can solve the problems with respect to making a seal portion thin, improving an assembling property, preventing a position shift, making a surface pressure low, making the surface pressure uniform, and the like, and a method of forming such the gasket, and another object of the present invention is to provide a method of forming a gasket which can stably form the gasket, has a comparatively simple structure of a metal mold apparatus and has a comparatively short cycle time.